1. Field of the Invention
The present invention relates to an oxygen-type bleaching composition, particularly a bleaching composition capable of safely bleaching even colored and figured cloths colored with a metal complex dye or a metal complex pigment.
2. Description of the Prior Art
Oxidation reactions are generally utilized for bleaching cloths for domestic and commercial purposes. In most cases, chlorine-containing bleaching agents are used. However, colored and figured cloths cannot be bleached safely with the chlorine-containing bleaching agents. Recently, oxygen-type bleaching agents capable of bleaching even colored and figured cloths have been used. However, it has been proved that the oxygen-type bleaching agents have insufficient safety for bleaching colored and figured (printed) cloths dyed with a metal-containing dye or pigment or treated with a metal salt or a metal-containing fixing agent.
General purpose bleaching compositions containing 50 to 100% of an inorganic peroxide sometimes cause color change and fading under usual treatment conditions (temperature: 40.degree.-60.degree. C., concentration: 0.3-1.0%), whereas bleaching compositions containing a surfactant, an inorganic peroxide and a builder (usually containing 10 to 50 weight % of an inorganic peroxide) do not cause color change or fading of colored and figured cloths under usual treatment conditions (temperature: 10.degree.-40.degree. C., concentration: 0.05-0.2 weight %). Thus, the color change and fading of colored and figured cloths are problems peculiar to the bleaching compositions containing a relatively high concentration (50 weight % or more) of an inorganic peroxide.
In the use of oxygen-type bleaching agents, there have been proposed various ideas for stabilizing the peroxide in the bleaching bath, preventing a fluorescent brightening agent from reduction in activity and preventing textile and fibers from deterioration. For example, there has been proposed the idea of adding a chelating agent or a magnesium salt for this purpose. However, those processes have disadvantages such that when colored and figured cloths dyed with a metal-containing dye or pigment or colored and figured cloths treated with a metal salt or a metal-containing fixing agent are bleached by those processes, an extremely large amount of the peroxide-stabilizing agent is required, the tints of the cloths are changed or the effect of the addition of the chelating agent or magnesium salt is not exhibited.
After intensive investigations on those problems, the inventors found that the use of aminocarboxylic acid salts is relatively effective to ameliorate those problems.
However, it has also been found that the tendency of the aminocarboxylic acid salts to prevent the color change or fading is completely different from the tendency for stabilizing the peroxide. Namely, for stabilizing the peroxides used in the conventional processes, it has been desired to use a substance which chelates powerfully heavy metals which latter act as decomposition catalysts for the peroxides. However, for the prevention of color change or fading according to the present invention, a tendency opposite to said peroxide-stabilizing tendency has been recognized. Surprisingly, it has further been found that when a water softener is added to the aminocarboxylic acid salts, only nitrilotriacetic acid and its salts exhibit a specific excellent effect whereas the other aminocarboxylic acid salts do not exhibit said effect. The present invention has been completed on the basis of this finding.